A major aim of our work is to establish the nature of regulatory and catalytic mechanisms for enzyme reactions associated with glycogen metabolism. The next grant year we plan to further study (1) the relationship of the activity of phosphoylase kinase to its subunit structure, (2) the specificity of cyclic AMP-dependent protein kinase and phosphorylase kinase with synthetic peptides, (3) the action of phosphoprotein phosphatase with peptide substrates and the involvement of metal ions in its activity, (4) the chemistry of glycogen phosphorylase and the involvement of its coenzyme, pyridoxal phosphate, in catalysis and regulatory phenomena. Our studies involve physical and chemical measurement of highly purified enzyme forms from both liver and muscle tissue. We will initiate a study of glucan phosphorylase from potato for studies of the reaction mechanism.